A conventional cruise control device provides for control to maintain a traveling speed of a vehicle, i.e., a vehicle speed at a constant speed as a target, based upon an instruction of cruise control through an operation of a cruise control switch by a user (JP-A-8-216729).
In such a cruise control device, when a user desires to start the cruise control, the user operates an accelerator pedal to adjust an actual vehicle speed to a desired vehicle speed. Then, when the actual vehicle speed rises or falls to the desired vehicle speed, the cruise control switch is operated. Thereby, the cruise control device defines the vehicle speed at this moment as a target speed and thereafter performs the cruise control for making the actual vehicle speed follow the target vehicle speed. That is, output torque of an in-vehicle engine is feedback-controlled in accordance with a deviation between the actual vehicle speed and the target vehicle speed, thereby to automatically regulate the actual vehicle speed to the target vehicle speed. At the time of starting the cruise control, however, an initial value of the output torque of the in-vehicle engine is not defined in accordance with the deviation between the actual vehicle speed and the target vehicle speed.
There is, therefore, conventionally proposed a cruise control device, in which a value, at the time of cruise starting, with respect to pedal torque as torque defined in accordance with an operation amount of the accelerator pedal is defined as an initial value of the output torque at the time of starting the cruise control. This is because the pedal torque at the time of the cruise starting is considered an appropriate torque for maintaining a vehicle speed at the time of starting the cruise control.
However, the cruise control device is adapted to set an actual vehicle speed at the time of operating the cruise control switch as a target vehicle speed even when the cruise control switch is operated in an acceleration state of a vehicle where the accelerator pedal is pressed down deep. In addition, torque in accordance with an operation amount of the accelerator pedal at the time of operating the cruise control switch is defined as an initial value of the torque of the in-vehicle engine at the time of the cruise starting. However, since the initial value of the torque in this case is the torque at the time of the accelerating, it will be greater than appropriate torque for maintaining the target vehicle speed. Accordingly, even after the cruise control is started, the acceleration of the vehicle continues for a little while, resulting in undesired drivability of a vehicle.